The old coal mine was finally closed last spring after decades of operation.

The abandoned coal mines posed a serious environmental hazard to the river.

The stray complaints from early users were a canary in a coal mine for the product team.

The sudden departures of our most outspoken employees were canaries in the coal mine, signaling deeper problems in the company culture.

The timid investors acted like canaries in a coal mine, fleeing the market at the first sign of trouble.

Climate researchers compared modern pollution sensors to canaries in coal mines, warning that small changes often signal larger dangers.

The neighborhood's increase in abandoned storefronts acted as a canary in the coal mine for the city's economic decline.